Safety switch for drill press using chuck key

Abstract

The subject safety switch insures that the chuck key has been removed from the chuck prior to operation of the drill press. A slide "on-off" switch is engaged by a guard that prevents the sliding movement necessary to turn the switch on. The guard of the safety switch is not part of the electrical circuit, but rather is a mechanical addition which prevents operation of the electrical circuit. The socket is formed in the housing adjacent the guard. The chuck key is inserted into the socket to engage the guard and remove it from the path of travel of the switch to permit the switch to be shifted between the on and off position. The socket is keyhole shaped, whereby insertion of the chuck key therein will force the chuck to seat within the lower narrower aperture thereof.

Having thus set forth the nature of the invention, what is claimed herein is: 
     
       1. A safety system for a drill operated by an electric motor journaled in a housing to rotate a bit-carrying chuck, said safety system comprising: a. a switch mounted in a side wall of the housing, and connected in circuit to actuate the motor,   b. the switch being slidable along a lineal path of travel to be moved between a normally "off" position at one end of its travel, and an "on" position at the other end of its travel,   c. a resilient guard means yieldably mounted in the housing,   d. the guard means intersecting the path of travel of the switch normally to prevent the switch from being moved along the lineal path of travel to force the switch to remain in the normally "off" position,   e. a socket formed in a side wall of the housing adjacent the guard means,   f. the socket including a pair of intersecting substantially circular apertures of different diameters, with the upper one larger than the lower one,   g. a chuck key having a shank terminating at one end in an enlarged pinion, and at the other end in a handle, and   h. the pinion end of the chuck key being inserted into the upper aperture with the shank substantially horizontal to define a first lineal motion, and the pinion end being moved vertically downwardly into the lower aperture to define a second lineal motion substantially perpendicular to the said first motion with the shank to remain horizontal, and to cause the pinion end to engage and to remove the guard means from the lineal path of travel of the switch whereby the switch is free to be actuated at will, while the chuck key is clamped in the lower aperture by its pinion end being entrapped between the lower aperture and the resilient guard.   
     
     
       2. The combination claimed in claim 1 wherein: a. the resilient guard includes a serpentine spring strip,   b. one end of the strip is mounted to the housing opposite the socket,   c. the wall of the socket having the enlarged diameter extends over the transverse leg of the strip opposite the mounting thereof,   d. a second leg of the strip extends across the socket for engagement by the chuck key upon its insertion into said socket,   e. the end of the strip opposite the mounting thereof is a short transverse leg which acts to block the travel of the switch whereby on attempting to slide the switch from the "off" to the "on" position the physical movement of the switch will shift the strip onto contact with the socket wall and prevent further motion of said switch, thus preventing the switch from being actuated.   
     
     
       3. The combination claimed in claim 1 wherein: a. the outer wall of the socket is vertical and the inner wall of the socket is sloped downwardly and away from the spring strip to define a camming surface which self-supportingly holds the pinion of the chuck key after insertion thereof.